Slit-scan photography works much like a rolling shutter does—the sensor continually collects image data but the shutter never actually closes, hence its use in determining a "photo finish"—whatever crosses the camera's view first, appears first in the photo set. Or at least that's how its supposed to work.

Beautiful cycling photo finish with lots of bikes

Note how the backs of the cyclists are sometimes in an exaggerated arc as the vertical movement of them pedaling, over time is captured in a single frame.

Lunging photo finish in cross country skiing

Note the bending of the ski poles due to vertical movement.

Turntable portrait with slit-scan camera iPhone app

You can try this at home.

2001 A Space Odyssey: Unwrapping the Slit Scan sequences

This site shows an attempt to reverse the distorting affects of slit scan images as used in the movie 2001, in order to decipher them. The results are far from conclusive but you can see some things that are less abstract.